The present invention relates to a disc apparatus, in particular, relates to a disc apparatus for reading information from and/or recording information to a recording medium such as a flexible magnetic disc.
A construction of one example of flexible magnetic disc apparatus (such apparatus will be referred to as simply "magnetic disc apparatus" hereinafter) will now be described with reference to FIGS. 1 and 2.
A flexible magnetic disc (this disc will be referred to as simply "disc" hereinafter) 3 is, as known, enclosed in an enclosing case 4. In FIGS. 1 and 2, the magnetic disc apparatus 1 has a holder 5 located above a frame 2 thereof. The enclosing case 4 (this case is indicated with chain lines in the figures) will be inserted into the holder 5.
The magnetic disc apparatus 1 has a construction by which, with the known art, the holder 5 will operate as follows. The holder will be lowered, in FIG. 2, in response to the enclosing case 5 being inserted into the magnetic disc apparatus 1. Conversely, the enclosing case 4 will be ejected as a result of the holder 5 being raised. The movements indicated by the terms "lowering" and "raising" are with respect to the directions in FIG. 2, hereinafter.
The magnetic disc apparatus 1 has a known mechanism by which magnetic heads 10 and 12 access the disc 3 in response to the movement of the holder 5. The movement of the holder 5 is the holder 5 being lowered. Conversely, by this mechanism, the magnetic heads 10 and 12 go away from the disc 3 in response to the movement of the holder 5. The movement of the holder 5 is the holder 5 being raised.
The holder 5 has a top plate 5a located on the top thereof. An opening 5b is provided in the top plate 5a into which a below-described magnetic head unit 8 is inserted.
The magnetic head unit 8 has the above-mentioned magnetic heads 10 and 12 which are used to read information from and/or to record information to an information track in the disc 3. A shutter lever 6, having a L-letter like shape, is provided on the top plate 5a. This shutter lever 6 effects opening a shutter (not shown in the figures) provided for on the enclosing case 4 in response to the enclosing case 4 being inserted into the magnetic disc apparatus 1.
This shutter lever 6 is pivotably supported on the top plate 5a. The shutter provided on the enclosing case 4 has the following known features. The shutter effects protecting the disc 3. This shutter has to be opened so as to make the opening on the enclosing case 4. Thus, through the made opening, the magnetic heads 10 and 12 may access the disc 3 enclosed in the enclosing case 4. This accessing by means of the magnetic heads 10 and 12 enables them to read information from and/or to record information to an information track formed on the disc 3.
The shutter lever 6 is always biassed, in the clockwise direction in FIG. 1, by means of a coil spring 7 with its pulling force. This biassing in the clockwise direction results in closing, by means of the shutter lever 6, the shutter of the enclosing case 4 when the enclosing case 4 is inserted into the holder 5. An engaging pin 6a projects from the top of the shutter lever 6. This projection of the engaging pin 6a is directed toward into the inside of the holder 5 through an opening 5c having an arc shape. This direction corresponds to that toward the reverse side of the sheet on which FIG. 1 is represented. This engaging pin 6a engages the shutter of the enclosing case 4 so as to open the shutter.
The above-mentioned magnetic head unit 8 has the following construction. The magnetic head unit 8 comprises a carriage 9 provided slidably in radial directions of the disc 3. This radial directions respectively correspond to the directions A and B shown in FIG. 1. As shown in FIG. 2, the lower magnetic head 10 is mounted on the top surface near the left end of the carriage 9. An arm 11 is up-and-down swingably supported on the right end post 9a of the carriage 9. The upper magnetic head 12 is mounted on the bottom surface of the left end of the arm 11.
The carriage 9 engages with a lead screw (not shown in the figures) which is driven by a stepper motor (not shown in the figures). With this engagement, the carriage may be moved in either the directions A or B in response to the turning of the lead screw. This movement of the carriage 9 enables
the magnetic heads 10 and 12 moving on the disc 3 in its radial directions.
The arm 11 is biassed in the direction C shown in FIG. 2 by means of a torsion spring 9c, shown in FIG. 1, with its pressing force. This torsion spring 9c is mounted on the post 9a of the carriage 9. An abutting bar 11a projects from the left side of the arm 11 as shown in FIG. 1. This abutting bar 11a abuts-on the top plate 5a of the holder 5. In this construction, when the enclosing case 4 is to be ejected from the magnetic disc apparatus 1 (the state of the magnetic head apparatus i in which the enclosing case 4 has been ejected will be referred to as "disc unloading state" hereinafter), the magnetic disc apparatus 1 operates as follows.
Then, as mentioned above, the holder 5 is raised and the enclosing case is thus ejected. The arm 11 is raised upward in FIG. 2 as a result of being pushed by means of the raised holder 5. This pushing the arm 11 is effected through the abutting bar 11a. That is, the top plate 5a of the holder 5 pushes the abutting bar 11a so as to raise the arm 11. Thus, the arm 11 is raised against the reverse-direction pushing force applied by means of the torsion spring 9c. As a result, the upper magnetic head 12 is raised. Thus, the upper magnetic head 12 goes away from the lower magnetic head 10.
The state of the magnetic disc apparatus 1 in which the enclosing case 4 is loaded in the apparatus 1 as a result of the enclosing case 4 having been inserted therein will be referred to as "disc loading state" hereinafter.
When the magnetic disc apparatus 1 moves from the disc unloading state to the disc loading state thereof, the holder 5 is lowered as mentioned above. Thus, the top plate 5a is lowered. As a result, the effect having been performed on the abutting bar 11a by means of the top plate 5a is released accordingly. This effect is to maintain the abutting bar 11a at the raised position thereof. Thus, the arm 11 is lowered by means of the torsion spring 9c with its pushing force. Thus, the upper magnetic head 12 is lowered. Thus, the upper magnetic head 12 approaches the lower magnetic head 10. As a results, both the upper and lower magnetic heads 10 and 12 together sandwich the disc 3.
Generally speaking, a magnetic disc apparatus for recording information to and/or reading information from a flexible magnetic disc has the following features. In such a magnetic disc apparatus, for example, in the magnetic disc apparatus 1 as mentioned above, the magnetic disc 1 is a recording medium which may be changed by another similar disc. That is, the disc 3 loaded in the magnetic disc apparatus 1 may be replaced by another disc as occasion demands. That is, the disc 3 may be ejected so as to be unloaded from and another disc may be inserted so as to be loaded into the magnetic apparatus 1.
Generally speaking, such a magnetic disc apparatus, for example, the magnetic disc apparatus 1, even in the disc unloading state, may operate as follows. The magnetic disc apparatus 1 executes seeking action according to a corresponding command provided from a host apparatus or a mother apparatus thereof. This seeking action is performed by moving the heads 10 and 12 in the directions which would correspond to radial directions of a disc if the disc were loaded therein. The host apparatus or the mother apparatus comprises for example, a computer utilizing the magnetic disc apparatus 1 as means for recording and/or reading information associated with the computer.
Further, actions executed in a such a magnetic disc apparatus will be referred to as "head loading/unloading action" or "head loading/unloading movement". These actions are respectively those that the heads, in the example, the heads 10 and 12 approach/go away from each other, in directions substantially perpendicular to the information recording surface of the disc 3.
A reason of such seeking action being to be executed even during the disc unloading state will now be described. By moving the heads 10 and 12 prior to the disc 3 being loaded in the magnetic disc apparatus 1, it is possible to generate a condition at a moment the disc 3 is loaded. The condition to be generated is a preparation for a process to be performed on the disc 3 and the condition is that the heads 10 and 12 are on the so-called #00 tracks formed on the disc 3. Such generating of a condition as a preparation for a process to be performed on a disc is, in other word, initializing of the heads. Such initialization of the heads being executed before the disc is loaded in the magnetic disc apparatus enables the host apparatus to execute the process of using the magnetic disc apparatus with the disc without any delay time or idling time.
Such seeking action being executed in its disc unloading state needs the following operation in the magnetic disc apparatus 1. As mentioned above, the upper magnetic head 12 is raised when the disc 3 is being ejected. For this purpose, the abutting bar 11a of the arm 11 is pushed upward by means of the top plate 5a of the holder 5. Thus, this condition is maintained during its disc unloading state. That is, in this condition, the abutting bar 11a is pushed upward by means of the top plate 5a.
The above-mentioned seeking action by the heads 10 and 13, which are the parts of the magnetic head unit 8, has to be executed in this condition. Thus, the magnetic head unit 8 has to move in this condition. That is, the abutting bar 11a, which is the part of the magnetic head unit 8 as mentioned above, has to slide on the top plate 5a which pushes the abutting bar 11a. As a result, considerable friction occurs between the abutting bar 11a and the top plate 5a during this seeking action. The friction force in this friction occurring corresponds to the pushing force resulting from the pushing of the abutting bar 11a by means of the top plate 5a.
This pushing of the abutting bar 11a by means of the top plate 5a is executed in the disc unloading state but is not executed in the disc loading state. Thus, an extra force is needed to execute the seeking action in the disc unloading state in comparison to that in the disc loading state. To provide this extra force, the stepper motor needs extra capacity in driving the magnetic head unit 8. This extra capacity in the stepper motor is not needed in the seeking action in the disc loading state. This extra capacity in the stepper motor may generally raise an electric power consumption amount in driving the stepper motor and may raise a noise level in this driving, unnecessarily.